GUSTATORY SENSILL^ 



133 



They include tlie styloconic sensillte found abundantly on the 

 proboscis in many Lepidoptera, and several types of hair-like 

 organs found on the mandibles, maxillae, palpi, etc., of different 

 insects. They are abundant, for example, on the mouth-parts of 

 the hive bee, but Mclndoo (1916) concludes that the thickness of 

 their cuticular covering precludes their performing any gustatory 

 function, and that they are more probably tactile organs. This 

 observer maintains that the only sensillae present in the bee which 

 function as chemoreceptors are the so-called " olfactory pores." 

 These, he states, are olfactory in function, as their name implies, 



1^ 



■I ^ T-- I 



\2^^ 



P ^ 



B 



Fig. 58. A, cross-section of apparatus used by Miniiich. B, The 

 arrows 1, 2, 3 represent the positions in which the insects were 

 tested, the walking legs being indicated by crossbars. Explana- 

 tion of lettering in the text. (Adapted from Minnich.) 



and he finds no evidence of true gustatory organs being present. 

 There is the perennial difficulty, however, of advancing sufficient 

 experimental proof that sensillae located on the mouth-parts 

 perceive taste and smell as separate impressions. Opinion is 

 inclining to the view that they are probably chemoreceptors, in 

 the broad sense, which are capable of appreciating stimuli both by 

 actual contact (taste) and at a distance (smell). 



The experiments of Minnich (1921) indicate that certain butter- 

 Hies (Pyrameis atalanta, Vanessa antiopa) are able to respond to 

 non-volatile substances by means of the tarsi of the middle and 

 hind pairs of legs. The apparatus (Fig. 58) used consisted of a 

 square wooden platform iv, bearing two cross-pieces iX, y, which 

 supported a tightly stretched wire screen s. The dimensions of 



